Disklike recording media, a method for detecting forged disks, an anti-forgery system for performing a true-false judgement based on information collected from the recording media, and a manufacturing apparatus for recording information in the disks

ABSTRACT

A recording medium includes first information selected from a plurality of information patterns and second information selected from another plurality of information patterns for the true-false judgement. A true-false judging device performs a statistic analysis when any coincidence is found between the readout combination of the first and second information and registered combination patterns, to identify an inspected recording medium as a forged product based on the result of the statistic analysis.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to disklike recording media, suchas CD (i.e., compact disk) and DVD (i.e., digital video disk or digitalversatile disk), which are suitable for mass production and wide-arealdistribution. More specifically, the present invention relates to ananti-forgery system, and related detecting apparatuses installable inthe distribution channel or in a center office equipped with a hostcomputer. Moreover, the present invention relates to a manufacturingmethod and apparatus for recording the information for a true-falsejudgement on the surfaces of the disk.

[0002] The conventional CD is preferably used for recording the audioinformation or program. The conventional VHD or LD is preferably usedfor recording video or image information. However, a recently developedDVD has a very large recording capacity which is approximately 5 to 7times the recording capacity of the above-described conventional disks.Thus, the CD, VHD and LD will be replaced by DVD-Audio and DVD-Video.

[0003] In other words, the high-density recording media can provide anadded value due to their large recording capacity. On the other hand,the industrial damage and monetary loss will be very large if they aresubjected to the forgery.

SUMMARY OF THE INVENTION

[0004] An object of the present invention is to provide an anti-forgerysystem capable of accurately detecting forged products of the disklikerecoding media at an earlier stage of the circulation of the forgedproducts.

[0005] In order to accomplish the above and other related objects, oneaspect of the present invention provides a recording medium comprisingfirst information selected from a plurality of information patterns fora true-false judgement, and second information selected from anotherplurality of information patterns for the true-false judgement.

[0006] Preferably, the recording medium has a disklike body with a firstsurface on which the first information is recorded and a second surfaceon which the second information is recorded. In this case, the firstinformation may be a pit or groove pattern formed on the first surface.A registered combination pattern of an enciphered format may be recordedon a specific area of a disk surface other than the first informationand the second information. The first information and the secondinformation are combined randomly.

[0007] Another aspect of the present invention provides a system fordetecting forged products of recording media. This system comprises areading means for reading first information and second information froman inspected recording medium, a memory means for storing a plurality ofregistered combination patterns for a true-false judgement, and atrue-false judging means for identifying the inspected recording mediumas a forged product when no coincidence is found between a readoutcombination of the first and second information and the registeredcombination patterns.

[0008] Preferably, the true-false judging means is for furtherperforming a statistic analysis when any coincidence is found betweenthe readout combination and the registered combination patterns, therebyidentifying the inspected recording medium as a forged product based onthe result of the statistic analysis.

[0009] Preferably, in the statistic analysis, the true-false judgingmeans is for detecting a combination pattern of the first and secondinformation recorded on the forged product with reference to a standarddeviation or a time differential value of the standard deviation.

[0010] Another aspect of the present invention provides an apparatus fordetecting forged products of recording media. This apparatus comprises areading means for reading first information and second information froman inspected recording medium, a transmitting means for transmitting areadout combination of the first and second information to a true-falsejudging apparatus, a receiving means for receiving a true-falsejudgement result from the true-false judging apparatus, and an outputmeans for outputting the true-false judgement result.

[0011] Preferably, the readout combination of the first and secondinformation is transmitted to the true-false judging apparatus by usinga communication device and related communication software. The apparatusmay be a playback apparatus of the disklike recording medium.

[0012] Another aspect of the present invention provides an apparatus fordetecting forged products of recording media. This apparatus comprises amemory means for storing a plurality of registered combination patternsfor a true-false judgement, a receiving means for receiving acombination of first and second information read out from an inspectedrecording medium, and a true-false judging means for identifying theinspected recording medium as a forged product when no coincidence isfound between the readout combination of the first and secondinformation and the registered combination patterns.

[0013] In this case, the true-false judging means is for furtherperforming a statistic analysis when any coincidence is found betweenthe readout combination and the registered combination patterns, so asto identify the inspected recording medium as a forged product based onthe result of the statistic analysis. The true-false judging means isfor detecting a combination pattern of the first and second informationrecorded on the forged product with reference to a standard deviation ora time differential value of this standard deviation.

[0014] Moreover, another aspect of the present invention provides amanufacturing apparatus for a disklike recording medium. Thismanufacturing apparatus comprises a first recording means for recordingmain information including first information on a first surface of thedisklike recording medium, and a second recording means for recordingsecond information on a second surface of the disklike recording medium.Each of the first and second information is selected from a plurality ofinformation patterns for a true-false judgement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects, features and advantages of thepresent invention will become more apparent from the following detaileddescription which is to be read in conjunction with the attacheddrawings, in which:

[0016]FIG. 1 is a perspective view showing a recording disk and anapparatus for detecting forged products in accordance with a preferredembodiment of the present invention;

[0017]FIG. 2 is a view illustrating an example of combined true-falsejudging information to be recorded in the disk shown in FIG. 1;

[0018]FIG. 3 is a block diagram showing an essential arrangement of aforged product detecting system in accordance with the preferredembodiment of the present invention;

[0019]FIG. 4 is a flowchart illustrating the details of a true-falsedetection in accordance with the preferred embodiment of the presentinvention;

[0020]FIG. 5 is a view illustrating an example of the statisticprocessing for counting the agreement of the combination of thetrue-false judging information in accordance with the preferredembodiment of the present invention;

[0021]FIG. 6 is a histogram showing the relationship between the type ofdisk and its occurrence;

[0022]FIG. 7 is a histogram showing the relationship between the type ofdisk and its occurrence;

[0023]FIG. 8 is a histogram showing the relationship between the type ofdisk and its occurrence;

[0024]FIG. 9 is a histogram showing the relationship between the type ofdisk and its occurrence;

[0025]FIG. 10 is a graph showing the history of the variation in thestandard deviation;

[0026]FIG. 11 is a graph showing the history of the variation in thetime differential value of the standard deviation;

[0027]FIG. 12 is a view showing a relationship between a distributionchannel of disks and a forged product detecting system in accordancewith the preferred embodiment of the present invention;

[0028]FIG. 13 is a flowchart showing the processing performed at aterminal of the wholesale or retail shop shown in FIG. 12 in accordancewith the preferred embodiment of the present invention;

[0029]FIG. 14 is a flowchart showing the processing performed in adistribution administrating center shown in FIG. 12 in accordance withthe preferred embodiment of the present invention;

[0030]FIG. 15 is a flowchart showing the processing performed at aterminal of a customer shown in FIG. 12 in accordance with the preferredembodiment of the present invention;

[0031]FIG. 16 is a flowchart showing another processing performed in thedistribution administrating center shown in FIG. 12 in accordance withthe preferred embodiment of the present invention;

[0032]FIG. 17 is a view showing another relationship between thedistribution channel of the disks and a forged product detecting systemin accordance with the preferred embodiment of the present invention;

[0033]FIG. 18 is a side cross-sectional view showing a compact disk inaccordance with the preferred embodiment of the present invention;

[0034]FIG. 19 is a side cross-sectional view showing a digital versatiledisk in accordance with the preferred embodiment of the presentinvention;

[0035]FIG. 20 is a side cross-sectional view showing another digitalversatile disk in accordance with the preferred embodiment of thepresent invention;

[0036]FIG. 21 is a side cross-sectional view showing another digitalversatile disk in accordance with the preferred embodiment of thepresent invention;

[0037]FIG. 22 is a side cross-sectional view showing a read only HDTVdisk in accordance with the preferred embodiment of the presentinvention;

[0038]FIG. 23 is a block diagram showing a disk manufacturing system inaccordance with the preferred embodiment of the present invention; and

[0039]FIG. 24 is a block diagram showing another disk manufacturingsystem in accordance with the preferred embodiment of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Hereinafter, preferred embodiments of the present invention willbe explained with reference to the attached drawings.

[0041]FIG. 1 is a perspective view showing a recording disk and anapparatus for detecting forged products in accordance with a preferredembodiment of the present invention. In FIG. 1, a disk 1 has a firstsurface on which main information is recorded. The main informationincludes a first image “A” which is used in a true-false judgement foreach disk. The disk 1 has a second surface on which a second image “B”is formed. The second image “B” is also used in the true-falsejudgement. The second image “B” and the main information including thefirst image “A” are read by a CCD line sensor 2 and a pickup lens 3,respectively. The data on the disk 1 is scanned when the disk 1 isrotating while the CCD line sensor 2 and the pickup lens 3 arestationarily fixed. The CCD line sensor 2 and the pickup lens 3,cooperatively serving as a reading device, can be replaced by any otheroptical, magnetic, magneto-optical, or capacitance sensors or deviceshaving the equivalent function. The images “A” and “B” can be replacedby any other bar codes, characters, enciphered codes when the readingdevice can read or discriminate them. The true-false judgementinformation may be scrambled or mixed with other information so as notto be discriminable at a glance.

[0042]FIG. 2 shows simple samples of the true-false judgementinformation. The first image “A”, serving as main information, is amammoth portrait. The second image “B”, serving as print information, isa clover mark. A total of five different patterns are prepared for eachof the first and second images “A” and “B,” so that one of them isarbitrarily selected as a true-false judgement information. According tothis embodiment, the first image “A” is selectable from the groupconsisting of the mammoth, elephant, giraffe, ant eater, and horseportraits. The second image “B” is selectable from the group consistingof the clover, four-leaf clover, heart, spade, and diamond marks.Accordingly, this embodiment provides 25 (=5×5) patterns as theregistered or authorized combinations of the first and second images “A”and “B.” In other words, the pattern recorded in each disk 1 is one ofthe 25 registered or authorized patterns, with each pattern having anequal possibility (i.e., 1/25) to be selected.

[0043] The first images “A” may resemble each other but different insome portions so that the third party cannot find the difference betweenthem. Similarly, the second images “B” may resemble each other butdifferent in some portions.

[0044]FIG. 3 is a schematic arrangement of a forged product detectingsystem. A main information reading section 4 reads the main information(i.e., first image “A”) recorded on the disk 1. A print informationreading section 5 reads the print information (i.e., second image “B”)printed on the disk 1. Each readout image is processed by using anappropriate image recognition software (not shown). A true-false judgingsection 6 receives the first image “A” from the main information readingsection 4 and the second image “B” from the print information readingsection 5. Based on a combination of the readout images “A” and “B”, thetrue-false judging section 6 performs first and second true-falsejudgements shown in FIG. 4. The true-false judging section 6 comprises aCPU 10 performing the true-false judgements, and associated memories ROM11 and RAM 12. The ROM 11 stores a total of 25 registered or authorizedpatterns α (i.e., 11, 12, 13, - - - ,54, 55) as possible combinations ofthe first and second images “A” and “B.” Furthermore, the ROM 11 storesa rule β for judging the circulation of forged products. The RAM 12stores the history of readout combined image patterns by counting theoccurrence of respective patterns 11, 12, 13, - - - ,54, 55.

[0045] In the flowchart shown in FIG. 4, the initialization is performedin a step S1. Then, the images “A” and “B” are read from the disk 1 tobe inspected in a step S2. Then, the true-false judging section 6performs the first true-false judgement. More specifically, thecombination of the readout images “A” and “B” is compared with the imagepatterns α stored in the ROM 11 in a step S3. If no coincidence is found(NO in the step S3), it is concluded in a step S4 that the inspecteddisk 1 is a forged product. If any coincidence is found (YES in the stepS3), the true-false judging section 6 performs the second true-falsejudgement. More specifically, in a step S5, the detected combination ofthe readout images “A” and “B” is classified into the corresponding oneof the 5×5 patterns of the image patterns α. Then, in a step S6, the RAM12 increments a count value of the identified pattern as shown in FIG.5. At the same time, a total disk number “N” is increased by 1. Then,the updated classification data is statistically processed in a step S7.

[0046]FIG. 6 is a histogram showing the relationship between the patternof disk and the frequency of occurrence which is typically observed inan initial stage of the circulation of disks (e.g., N=250). FIG. 7 is ahistogram showing the occurrence of the disk patterns observed when thetotal disk number “N” is increased (e.g., N=2,500). As apparent fromFIG. 7, the frequency of occurrence in each disk pattern issubstantially uniform when the 25 patterns are randomly used.

[0047] It is now assumed that circulation of forged products is startedafter the passage of a significant leading time. Many of the forgedproducts contain the main information with no (or incomplete) printinformation. This kind of forged products can be easily checked by theabove-described first true-false judgement. However, the firsttrue-false judgement is no longer reliable when the forged products haveperfect print information. In such a case, the circulation of the forgedproducts can be detected by the increase of a particular disk pattern.

[0048]FIG. 8 is a histogram showing the occurrence of the disk patternsobserved when the total disk number “N” is further increased (e.g.,N=7,500). In this case, the occurrence of the pattern “43” is largerthan other patterns by approximately 50. This is a sort of signindicating the presence of forged products. From this sign, it isbelieved the circulation of forged products has just begun. On the otherhand, this may be an accidental phenomenon.

[0049] Accordingly, in the step S7 of the flowchart shown in FIG. 4, thestatistic analysis is performed to confirm the presence of the forgedproducts. For example, the circulation of the forged products isconfirmed when the occurrence n_(ij) of a specific disk pattern (ij) islarger than the average occurrence n₀ of other patterns by apredetermined threshold. The rule β stored in the ROM 11 determines thispredetermined threshold (e.g., 3σ). Thus, in a step S8, it is checkedwhether the value (n_(ij)-n₀) is equal to or larger than 3σ, where σrepresents a standard deviation. The occurrence n₄₃ of the pattern “43”shown in FIG. 8 does not yet exceed 3σ. Thus, the decision of the forgedproduct circulation is postponed in a step S9.

[0050]FIG. 9 is a histogram showing the occurrence of the disk patternsobserved when the total disk number “N” is 12,500. In this case, theoccurrence n₄₃ of the pattern “43” is larger than the average occurrencen₀ of other patterns by approximately 800. The difference 800 issufficiently larger than 3σ. Thus, it is concluded that approximately800 forged products have been already circulated in the market at thistiming (step S10).

[0051] Although the above-described threshold (e.g., 3σ) is read outfrom the ROM 11, it is possible to arbitrarily modify the readoutthreshold according to the intent of the user. For example, thethreshold based on the rule β can be modified considering the total disknumber “N.” Therefore, the judgement of the forged products may be madewhen the number of disks having a certain pattern exceeds 800 withrespect to the total disk number N=13,300. If the threshold is reducedto 2σ, the forged products will be detected at an earlier stage althoughthe accurateness in the true-false judgement will be worsened.

[0052] It is preferable to monitor the statistic data periodically foreach of the patterns (i. e., 5×5=25 patterns). FIG. 10 shows the changeor transition of the standard deviation σ in relation to the passage oftime (date), which is observed on a certain pattern. The noise rate ishigh in the initial stage since the total number of the disks circulatedin the market is small. Accordingly, it is preferable to cancel thejudgement during the initial stage (i.e., during the noise period). Thestandard deviation σ then decreases and stabilizes at a constant valueafter the noise period has passed. In other words, the time differentialvalue of the standard deviation (i.e., dσ/dt) gradually converges at 0as the total disk number increases. However, once the forged productsstart circulating in the market, the standard deviation σ startsincreasing correspondingly. Its time differential value dσ/dt alsoincreases rapidly toward a positive direction. Thus, the circulation ofthe forged products is sensitively detectable based on the timedifferential value dσ/dt. Furthermore, although the system may becomplicated, it will be possible to detect the presence of the forgedproducts by statistically monitoring the publication of the disk 1 withreference to the standard deviation σ and its differential value dσ/dt.

[0053] Accordingly, this embodiment makes it possible to surely detectthe forged products regardless of sophistication in the forgingtechnology. Furthermore, it is possible to accurately specify thepattern assigned to the forged disk. Only the software maker and theauthorized manufactures can know the details of the first image “A” andthe second image “B” and their combination patterns. It is impossiblefor the third parties to manufacture a great amount of forged productswithout being checked by the above-described true-false judgements. Evenif the third parties know the presence of the first and second images“A” and “B”, it will take a long time to analyze the details of theconcealed disk patterns and distribution ratio of each combination andwill be necessary to invest a great amount of money to prepare the samepatterned disks.

[0054] Although 25 (=5×5) patterns are prepared for the images “A” and“B” in the above-described embodiment, it is possible to change thenumber of combinations. Increasing the total number of combinations iseffective to detect forged products in an earlier stage. Although theprepared patterns are randomly or uniformly assigned to the disks in theabove-described embodiment, it is possible to intentionally change thedistribution ratio of each combined disk patterns. For the thirdparties, analyzing the intentionally-determined distribution ratio willbe a more-complicated and time-consuming work.

[0055]FIG. 12 shows a distribution channel of the disk 1 when the disk 1is a read-only disk, such as CD or DVD. A software maker 101, who is acopyright holder, produces the software to be distributed. A diskmanufacturer 102 produces the disks 1 in response to the request fromthe software maker 101. The mass produced disks 1 are sent to awholesaler 103. The wholesaler 103 distributes the disks 1 to a retailer104, such as a software shop, a disk shop, a record shop, or an electricappliance shop. A customer 105 buys the disk 1 at the retailer 104. Theforger 106 invades somewhere in this distribution channel to circulatethe forged products.

[0056] The true-false detecting apparatus performing the processingshown in FIG. 4 is placed in each of the wholesaler 103 and the retailer104 to detect the forged products by checking all or part of the diskshandled by them. Accordingly, the presence of the forged products isnotified from the wholesaler 103 or the retailer 104 to the softwaremaker 101 or the disk manufacturer 102. A distribution administratingcenter 100 collects the information from the true-false detectingapparatus installed in each of the wholesaler 103 and/or the retailer104. Accordingly, the presence of the forged products is checked by thedistribution administrating center 100. Establishing the distributionadministrating center 100 is advantageous when the disks are distributedthrough numerous franchised shops which may be located nationwide orworldwide. It will be easy to check a wide-area circulation of theforged products.

[0057] In the arrangement shown in FIG. 12, the distributionadministrating center 100 communicates with the terminals (i.e., thetrue-false detecting apparatuses) in the wholesaler 103 and/or theretailer 104 via radio or cable communication lines.

[0058]FIG. 13 is a flowchart showing the processing performed in eachterminal of the wholesaler 103 and/or the retailer 104. First, in a stepS11, the initialization is performed. Then, in a step S12, the images“A” and “B” are read from the disk 1 to perform the true-falsejudgement. Then, in a step S13, the communication line is connectedbetween the terminal and the distribution administrating center 100. Ina step S14, the detected combination of the images “A” and “B” istransmitted to the distribution administrating center 100. Thedistribution administrating center 100 checks the received informationwith the registered data. Then, the distribution administrating center100 returns the inspection result to the terminal. Thus, in a step S15,the terminal receives an answer signal of “YES” or “NO” returned fromthe distribution administrating center 100. Then, in a step S16, theterminal notifies an operator of the true-false judgement result througha display unit.

[0059]FIG. 14 is a flowchart showing the processing performed in thedistribution administrating center 100. The distribution administratingcenter 100 comprises CPU 10, ROM 11 and RAM 12 having the same functionsas those of the true-false judging section 6 disclosed in FIG. 3. Thedistribution administrating center 100 receives the information from theterminal in a step S20 to perform the first true-false judgement. Thecombination of the images “A” and “B” transmitted from the terminal iscompared with the image patterns α, i.e., 25 (=5×5) patterns, stored inthe ROM 11 in a step S21. If no coincidence is found (NO in the stepS21), it is concluded that the inspected disk 1 is a forged product.Thus, in step S22, the distribution administrating center 100 returnsthe inspection result “NO” to the terminal (refer to the step S15 in theflowchart of FIG. 13).

[0060] If any coincidence is found (YES in the step S21), thedistribution administrating center 100 performs the second true-falsejudgement. More specifically, in a step S23, the detected combination ofthe transmitted images “A” and “B” is classified into the correspondingone of the 5×5 patterns of the image patterns α. Then, in a step S24,the RAM 12 increments a count value of the identified pattern as shownin FIG. 5. At the same time, a total disk number “N” is increased by 1.Then, the updated classification data is statistically analyzed in astep S25. For example, the circulation of the forged products isconfirmed when the occurrence n_(ij) of a specific disk pattern (ij) islarger than the average occurrence n₀ of other patterns by apredetermined threshold. The rule β stored in the ROM 11 determines thispredetermined threshold (e.g., 3σ). Thus, in a step S26, it is checkedwhether the value (n_(ij)-n₀) is equal to or larger than 3σ, where σrepresents the standard deviation. When the judgement result is “NO” inthe step S27, the decision of the forged product circulation ispostponed as the total number of the forged products is small. Thus, thedistribution administrating center 100 returns the inspection result“YES” to the terminal (refer to the step S15 in the flowchart of FIG.13). On the other hand, when the judgement result is “YES” in the stepS26, it is concluded that a significant amount of forged products havebeen already circulated in the market at this timing. Thus, in a stepS28, the distribution administrating center 100 returns the inspectionresult “NO” to the terminal.

[0061] According to the above-described embodiment, the distributionadministrating center 100, serving as a center office equipped with ahost computer, performs the first and second true-false judgements.There is no necessity of providing the memories 11 and 12 in eachterminal in the wholesaler 103 and the retailer 104. Accordingly, thesystem cost is inexpensive. The memories 11 and 12 storing the secretinformation can be safely managed at the center office which is isolatedfrom the market. The distribution administrating center 100 can beprovided for each manufacturer 102 or commonly used by a group ofmanufactures 102. It is preferable that the distribution administratingcenter 100 periodically transmits the information to manufactures 102 orsoftware makers 101. In this case, the information may include themanufactured amount of the disk 1, detailed allocation of thecombination patterns of the images “A” and “B”, and the presence of theforged products.

[0062] Returning to the actual market, there are some problems to besolved. For example, some of the forged products will circulate througha mail-order selling channel, a door-to-door selling channel, or astreet stall other than the retailer 104. An ill-intentioned retailer104 will not mind to unlawfully sell the forged disks. No information istransmitted to the distribution administrating center 100 since theterminals are not used in these cases.

[0063] To solve this kind of problems, the present invention proposes asystem including a modem and a communication software incorporated inthe disk recording/playback system of the customer 105 (FIG. 12).

[0064]FIG. 15 is a flowchart showing the processing performed in thedisk recording/playback system of the customer 105. First, in a stepS31, the initialization is performed. Then, in a step S32, the images“A” and “B” are read from the disk 1 to perform the true-falsejudgement. Then, in a step S33, the communication line is connected viathe modem between the disk recording/playback system and thedistribution administrating center 100. In a step S34, the detectedcombination of the images “A” and “B” is transmitted to the distributionadministrating center 100. The distribution administrating center 100checks the received information with the registered data. Then, thedistribution administrating center 100 returns the inspection result tothe terminal. Thus, in a step S35, the disk recording/playback systemreceives an answer signal of “GO” or “STOP” returned from thedistribution administrating center 100. Then, in a step S36, the diskrecording/playback system allows the playback of the disk 1 in responseto the “GO” signal and displays an error message or ejects the disk 1 inresponse to the “STOP” signal.

[0065]FIG. 16 is a flowchart showing the processing performed in thedistribution administrating center 100. The distribution administratingcenter 100 receives the information from the disk recording/playbacksystem in a step S40 to perform the first true-false judgement. Thecombination of the images “A” and “B” transmitted from the diskrecording/playback system is compared with the image patterns α, i.e.,25 (=5×5) patterns, stored in the ROM 11 in a step S41. If nocoincidence is found (NO in the step S41), it is concluded that theinspected disk 1 is a forged product. Thus, in step S47, thedistribution administrating center 100 returns the “STOP” signal to thedisk recording/playback system.

[0066] If any coincidence is found (YES in the step S41), thedistribution administrating center 100 performs the second true-falsejudgement. More specifically, in a step S42, the detected combination ofthe transmitted images “A” and “B” is classified into the correspondingone of the 5×5 patterns of the image patterns α. Then, in a step S43,the RAM 12 increments a count value of the identified pattern as shownin FIG. 5. At the same time, a total disk number “N” is increased by 1.Then, the updated classification data is statistically analyzed in astep S44. For example, the circulation of the forged products isconfirmed when the occurrence n_(ij) of a specific disk pattern (ij) islarger than the average occurrence n₀ of other patterns by apredetermined threshold. The rule β stored in the ROM 11 determines thispredetermined threshold (e.g., 3σ). Thus, in a step S45, it is checkedwhether the value (n_(ij)-n₀) is equal to or larger than 3σ, where σrepresents the standard deviation. When the judgement result is “NO” inthe step S45, the decision of the forged product circulation ispostponed as the total number of the forged products is small. Thus, thedistribution administrating center 100 returns the “GO” signal to thedisk recording/playback system (refer to the step S35 in the flowchartof FIG. 15). On the other hand, when the judgement result is “YES” inthe step S45, it is concluded that a significant amount of forgedproducts have been already circulated in the market at this timing.Thus, in a step S47, the distribution administrating center 100 returnsthe “STOP” signal to the disk recording/playback system (refer to thestep S35 in the flowchart of FIG. 15).

[0067] This system is applicable not only to so-called standalone typedisk recording/playback systems but also to built-in diskrecording/playback systems personal computers can be effectively used inthis case.

[0068] The above-described forged product detecting system can beflexibly modified according to the type of distribution channel. Forexample, as shown in FIG. 17, it is possible to connect each of thewholesaler 103, the retailer 104, and the customer 105 to thedistribution administrating center 100 via a unidirectionalcommunication line, instead of using the bidirectional communicationline. This system sufficiently works in roughly checking the circulatedcondition of the forged products.

[0069] The presently available cable communications, radiocommunications, analog lines and digital lines are usable for thecommunications in the above-described forged product detecting system.The high-speed digital lines, such as ISDN, are preferably used for thebidirectional communications. However, the analog lines will besufficient for the unidirectional communications. Regarding the lines,the direct connection is preferable. However, it is possible toestablish the communication line via the Internet or any othercommercially available communication network. The E-mail or telex willbe used in the unidirectional communication, since the time lag of fewdays will be allowed. Furthermore, when a product managing system isalready installed in the wholesaler 103 or in the retailer 104, thebidirectional communication function of the existing product managingsystem will be utilized for the forged product detecting system. Whenthe customer 105 likes the outdoor use of the playback system, aportable telephone or a similar handy phone will be used as acommunication device for transmitting the information to thedistribution administrating center 100.

[0070] Furthermore, when the information is sent from the wholesaler103, the retailer 104 or the customer 105 to the distributionadministrating center 100, it is preferable to add identification data,such as a code number, address, telephone number, and a network ID.These data will be effectively used in the succeeding procedureperformed in the distribution administrating center 100.

[0071] Hereinafter, the detailed arrangement of the disk 1 will beexplained with reference to cross-sectional views. FIG. 18 shows a CDincluding a substrate 201, a first recording layer 202 formed on thesubstrate 201, a protection layer 203 formed on the first recordinglayer 202, and a second recording layer 204. The main informationincluding the first image “A” is recorded in the first recording layer202. The second image “B” is recorded in the second recording layer 204.More specifically, the substrate 201 is a polycarbonate or acrylic orpolyolefine substrate having a thickness of 1.2 mm. The image “A” is afine pit or groove pattern formed on the upper surface of this substrate201 by stamping. The first recording layer 202 contains a metal selectedfrom the group consisting of aluminum, gold, silver, copper, titanium,chrome, nickel, tantalum, molybdenum, iron and silicon which has a highreflectivity, or their alloys. The protection layer 203 is, for example,made of a ultraviolet ray curable resin for protecting the firstrecording layer 202. The layer 204 is formed by screen printing oroffset printing to form the image “B.” The first recording layer 202 hasa lower transmissivity to prevent the leakage of information between thefirst recording layer 202 and the second recording layer 204.

[0072]FIG. 19 shows a DVD of 4.7 GB which has a bonded-substratestructure. The main information including the first image “A” isrecorded on a first substrate 201 a (0.6 mm thick). A first recordinglayer 202 is formed on the upper surface of the first substrate 201 a. Aprotection layer 203 is formed on the first recording layer 202. Asecond substrate 201 b (0.6 mm thick) is bonded on the protection layer203 via an adhesive layer 205 (e.g., ultraviolet ray curable type). Asecond recording layer 204, in which the second image “B” is formed, ispartly printed on the upper surface of the second substrate 201 b.

[0073]FIG. 20 shows another DVD of 4.7 GB which has a similarbonded-substrate structure. The main information including the firstimage “A” is recorded on the first substrate 201 a (0.6 mm thick). Thefirst recording layer 202 and the protection layer 203 are successivelyformed on the upper surface of the first substrate 201 a. On the otherhand, the second recording layer 204 is partly printed on the lowersurface of the second substrate 201 b (0.6 mm thick). A shielding layer206 is formed entirely along the lower surface of the second substrate201 b including the printed second recording layer 204 by white ink orwhole-surface screen printing. The protecting layer 203 and theshielding layer 206 are bonded by the adhesive layer 205 (ultravioletray curable type). The shielding layer 206 conceals the rolling patternspeculiar to the adhesive, thereby eliminating the reading error by theCCD line sensor 2.

[0074]FIG. 21 shows another DVD of 4.7 GB which has another similarbonded-substrate structure. The main information including the firstimage “A” is recorded on the first substrate 201 a (0.6 mm thick). Thefirst recording layer 202 and the protection layer 203 are successivelyformed on the upper surface of the first substrate 201 a. The secondimage “B” is formed on the lower surface of the second substrate 201 bby stamping. The second recording layer 204 is formed on the lowersurface of the second substrate 201 b. The second recording layer 204contains a metal selected from the group consisting of aluminum, gold,silver, copper, titanium, chrome, nickel, tantalum, molybdenum, iron andsilicon which has a high reflectivity, or their alloys. The firstrecording layer 202 and the second recording layer 204 are bonded by theadhesive 205 of adhesive sheet type. According to this arrangement, theCCD line sensor 2 can be replaced by the pickup lens 3. It is alsopossible to replace the first recording layer 202 by a semitransparentlayer, e.g., a thin metallic film or a thin dielectric layer. In thiscase, it becomes possible to read the information of the secondrecording layer 204 through the first recording layer 202 by the pickuplens 3 placed near the substrate 201. In other words, the total numberof the required sensors can be reduced to only one (i.e., single pickuplens 3).

[0075] The present invention is not limited to the above-described CDand DVDs, and therefore can be applied to MO disks, phase-change typedisks, and write once type disks. In this case, the first recordinglayer 202 is replaced by a conventional MO medium (e.g., a multilayeredstructure of SiO·TbFeCo·SiN·Al). The present invention can be applied toa multilayered disk having three or more information surfaces. In thiscase, the images “A” and “B” are arbitrarily disposed on selectedsurfaces. The thickness of the disk substrate is not limited to 0.6 mmor 1.2 mm.

[0076]FIG. 22 shows a read only HDTV (high-definition television) diskincluding a 0.8 mm substrate 201 on which the main information includingthe first image “A” is recorded. The first recording layer 202 and theprotection layer 203 are successively formed on the upper surface of thesubstrate 201. The second recording layer 204, in which the second image“B” is formed, is printed along the cylindrical side surface of thesubstrate 201 by bar-code printing or by stamping. According to thisarrangement, the protecting layer 203 has a free upper surface on whichanother substrate can be bonded to realize a high-density disk.

[0077] It is preferable that the image “A” is recorded by a specialrecording method so as not to be easily deciphered by the third parties.For example, the image “A” is recorded in a lead-in area, a lead-outarea, or a stamp area describing the disk number. It is also preferableto incorporate the image “A” as a low-frequency wobble signal into themain information. It is also preferable to incorporate the image “A” asan asymmetry variation of the RF signal. It is also possible toincorporate the image “A” as an electric watermark into the main imageor video information. Moreover, the present invention can be combinedwith any existing anti-forgery method.

[0078] Furthermore, instead of using the ROM 11, it is possible torecord the registered image patterns “α” in an enciphered format on aspecific area of the disk 1.

[0079]FIG. 23 shows a disk manufacturing facility for recording thefirst image “A” into the main information and printing the second image“B” to the disk 1. There are a total of five blank carrier manufacturinglines A1 to A5 each recording the main information including adesignated pattern of the image “A” on a blank disk. Similarly, thereare a total of five printing lines B1 to B5 each printing the designatedpattern of the image “B” on the disk 1. A connecting device 21,interposed between the blank carrier manufacturing lines A1˜A5 and theprinting lines B1˜B5, randomly connects one blank carrier manufacturingline to one printing line to manufacture the 25 patterned disks 1. It ispossible to interpose a mixing device 22 between the blank carriermanufacturing lines A1˜A5 and the connecting device 21, as shown in FIG.24.

[0080] This invention may be embodied in several forms without departingfrom the spirit of essential characteristics thereof. The presentembodiments as described are therefore intended to be only illustrativeand not restrictive, since the scope of the invention is defined by theappended claims rather than by the description preceding them. Allchanges that fall within the metes and bounds of the claims, orequivalents of such metes and bounds, are therefore intended to beembraced by the claims.

What is claimed is:
 1. A recording medium comprising: first informationselected from a plurality of information patterns for a true-falsejudgement; and second information selected from another plurality ofinformation patterns for the true-false judgement.
 2. The recordingmedium in accordance with claim 1, wherein said recording medium has adisklike body with a first surface on which said first information isrecorded and a second surface on which said second information isrecorded.
 3. The recording medium in accordance with claim 2, whereinsaid first information is a pit or groove pattern formed on said firstsurface.
 4. The recording medium in accordance with claim 2, wherein aregistered combination pattern of an enciphered format is recorded on aspecific area of a disk surface other than said first information andsaid second information.
 5. The recording medium in accordance withclaim 1, wherein said first information and said second information arecombined randomly.
 6. A system for detecting forged products ofrecording media, said system comprising: reading means for reading firstinformation and second information from an inspected recording medium;memory means for storing a plurality of registered combination patternsfor a true-false judgement; and true-false judging means for identifyingsaid inspected recording medium as a forged product when no coincidenceis found between a readout combination of said first and secondinformation and said registered combination patterns.
 7. The system inaccordance with claim 6, wherein said true-false judging means is forfurther performing a statistic analysis when any coincidence is foundbetween said readout combination and said registered combinationpatterns, thereby identifying said inspected recording medium as aforged product based on the result of the statistic analysis.
 8. Thesystem in accordance with claim 7, wherein said true-false judging meansis for detecting a combination pattern of said first and secondinformation recorded on the forged product with reference to a standarddeviation in said statistic analysis.
 9. The system in accordance withclaim 7, wherein said true-false judging means is for detecting acombination pattern of said first and second information recorded on theforged product with reference to a time differential value of a standarddeviation in said statistic analysis.
 10. An apparatus for detectingforged products of recording media, said apparatus comprising: readingmeans for reading first information and second information from aninspected recording medium; transmitting means for transmitting areadout combination of said first and second information to a true-falsejudging apparatus; receiving means for receiving a true-false judgementresult from said true-false judging apparatus; and output means foroutputting said true-false judgement result.
 11. The apparatus inaccordance with claim 10, wherein said readout combination of said firstand second information is transmitted to said true-false judgingapparatus by using a communication device and related communicationsoftware.
 12. The apparatus in accordance with claim 10, wherein saidapparatus is a playback apparatus of a disklike recording medium.
 13. Anapparatus for detecting forged products of recording media, saidapparatus comprising: memory means for storing a plurality of registeredcombination patterns for a true-false judgement; receiving means forreceiving a combination of first and second information read out from aninspected recording medium; and true-false judging means for identifyingsaid inspected recording medium as a forged product when no coincidenceis found between the readout combination of said first and secondinformation and said registered combination patterns.
 14. The apparatusin accordance with claim 13, wherein said true-false judging means isfor further performing a statistic analysis when any coincidence isfound between said readout combination and said registered combinationpatterns, thereby identifying said inspected recording medium as aforged product based on the result of the statistic analysis.
 15. Theapparatus in accordance with claim 14, wherein said true-false judgingmeans is for detecting a combination pattern of said first and secondinformation recorded on the forged product with reference to a standarddeviation in said statistic analysis.
 16. The apparatus in accordancewith claim 14, wherein said true-false judging means is for detecting acombination pattern of said first and second information recorded on theforged product with reference to a time differential value of a standarddeviation in said statistic analysis.
 17. A manufacturing apparatus fora disklike recording medium, said manufacturing apparatus comprising:first recording means for recording main information including firstinformation on a first surface of the disklike recording medium, saidfirst information being selected from a plurality of informationpatterns for a true-false judgement; and second recording means forrecording second information on a second surface of the disklikerecording medium, said second information being selected from anotherplurality of information patterns for the true-false judgement.